MEMS-based optical scanners are used in a variety of applications. For example, U.S. Pat. No. 7,952,781, whose disclosure is incorporated herein by reference, describes a method of scanning a light beam and a method of manufacturing a microelectromechanical system (MEMS), which can be incorporated in a scanning device.
As another example, U.S. Pat. No. 6,245,590 describes a MEMS scanning device with a variable resonant frequency. In one embodiment, an array of removable masses are placed on an exposed portion of an oscillatory body and selectively removed to establish the resonant frequency. A display apparatus includes the scanning device, wherein the scanning device scans about two or more axes, typically in a raster pattern. Various approaches to controlling the frequency responses of the scanning device are described, including active control of MEMS scanners and passive frequency tuning.
U.S. Patent Application Publication 2013/0207970, whose disclosure is incorporated herein by reference, describes a scanning depth engine, which includes a transmitter, which emits a beam comprising pulses of light, and a scanner, which is configured to scan the beam, within a predefined scan range, over a scene. The scanner may comprise a micromirror produced using MEMS technology. A receiver receives the light reflected from the scene and generates an output indicative of the time of flight of the pulses to and from points in the scene. A processor is coupled to control the scanner and to process the output of the receiver so as to generate a 3D map of the scene.
U.S. Patent Application Publication 2015/0260847, whose disclosure is incorporated herein by reference, describes a dual-axis scanning mirror, in which a scanning mirror assembly includes a support structure; a base, which is mounted to rotate about a first axis relative to the support structure; and a mirror, which is mounted to rotate about a second axis relative to the base. At least one rotor includes one or more permanent magnets, which are fixed to the scanning mirror assembly and which are positioned in an air gap of a magnetic stator so as to move in response to a magnetic circuit formed by the stator due to a driving electrical current.
PCT International Publication WO 2015/109273, whose disclosure is incorporated herein by reference, describes a scanning device, which includes a substrate, which is etched to define an array of two or more parallel rotating members, such as scanning mirrors, and a gimbal surrounding the rotating members. First hinges connect the gimbal to the substrate and define a first axis of rotation, about which the gimbal rotates relative to the substrate. Second hinges connect the rotating members to the support and define respective second, mutually-parallel axes of rotation of the rotating members relative to the support, which are not parallel to the first axis. In some embodiments, coupling means between the mirrors in the array couple the oscillations of the mirrors and thus maintain the synchronization between them.
Electrostatic comb drives are sometimes used in driving rotations of MEMS mirrors, with an appropriate electrical waveform applied to the comb drive in order to drive the mirror. In the regard, for example, U.S. Pat. No. 8,514,205 describes a drive circuit that includes a generator and a driver. The generator generates a signal having a period and a varying amplitude during a driving portion of the period. The driver is coupled to the generator and drives a plate of an electrostatically drivable plant with the signal. The drive circuit may be used to drive a mirror plate of a comb-drive MEMS mirror.